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Home My WebLink About20100752_R-2237C Modification additional questions_20161011 Carpenter,Kristi From:Shown, Marc T Sent:Tuesday, October 11, 2016 10:07 AM To:Wanucha, Dave Cc:Barrett, William A; Fisher, Paul F; Lauffer, Matthew S Subject:FW: R-2237C Modification additional questions Attachments:Rip Rap at pipe outlets.pdf Dave, We are using standard rip rap outlet pads at the outlets for these two pipes. Class ‘I’ rip rap has been called for instead of the standard class ‘B’ rip rap. The dissipater pads will be approximately 8’ long and 12’ wide. The D50 for class ‘I’ rip rap is 10” as opposed to 8” for class ‘B’. The weight of class ‘I’ rip rap is 105 lbs/cf. I am attaching a standard drawing. We have had minimal issues with these pads in the past. Due to the fact that these two sites will be difficult to access, post-construction, and their proximity to the stream it was determined that this was the most appropriate measure to take. As to the question of the sort of treatment that the stormwater is receiving the two sites differ. At the Bill’s Lane site the roadway drainage and drainage off of the cut slopes is being conveyed with shoulder berm gutter. This is due to the physical constraints of the project, a mountain on one side and a drop-off on the other. The final 80’ +/- of the outfall pipe at this site is laid at a relatively flat slope to help reduce the velocity and energy in the pipe. At the Blackberry Road site the roadway drainage is conveyed for the most part with grass lined ditches to inlets and then piped down Blackberry Road. The drainage along Blackberry Road is also conveyed through a storm drain system the conveys the flow between inlets through grass lined ditches. Let me know if you need anything further. Marc Marc Shown, PE NCDOT Hydraulics Unit From: Wanucha, Dave Sent: Monday, October 10, 2016 2:05 PM To: Shown, Marc T <mshown@ncdot.gov> Cc: Barrett, William A <wabarrett@ncdot.gov> Subject: RE: R-2237C Modification additional questions Hi Marc, A few more questions. What sort of treatment will the stormwater receive prior to entering the drainage pipes? Will there be riprap ditches, grass swales/ditches, concrete curb and gutter? Thanks. Dave W. Dave Wanucha Division of Water Resources 1 Transportation Permitting Unit NC Department of Environmental Quality 336-776-9703 office 336-403-5655 mobile Dave.Wanucha@ncdenr.gov NC DEQ Winston Salem Regional Office 450 West Hanes Mill Road, Suite 300 Winston Salem, NC 27105 Email correspondence to and from this address is subject to the North Carolina Public Records Law and may be disclosed to third parties. From: Wanucha, Dave Sent: Thursday, October 06, 2016 1:34 PM To: Marc T Shown (mshown@ncdot.gov) <mshown@ncdot.gov> Cc: Barrett, William A <wabarrett@ncdot.gov> Subject: R-2237C Modification additional questions Hi Marc, Would you send more detail relative to the riprap dissipater pads DOT plans to construct per the modification. I’m not seeing that BMP specifically referenced in DOT’s Stormwater BMP Toolbox. We’re wanting to review the pad square footage (length and width) size of bedrock and any other pertinent construction details. Also, an explanation of the extent of stormwater treatment achieved. Thanks for your help. Dave W. Dave Wanucha Division of Water Resources Transportation Permitting Unit NC Department of Environmental Quality 336-776-9703 office 336-403-5655 mobile Dave.Wanucha@ncdenr.gov NC DEQ Winston Salem Regional Office 450 West Hanes Mill Road, Suite 300 Winston Salem, NC 27105 2 Email correspondence to and from this address is subject to the North Carolina Public Records Law and may be disclosed to third parties. Email correspondence to and from this sender is subject to the N.C. Public Records Law and may be disclosed to third parties. 3